Thread rolling device



C. H. LAEMMEL THREAD ROLLING DEVICE .lj zo April 26, 1960 Filed Jan. 6, 1954 INVENTOR. C

April 26, 1960 c. H. LAEMMEL THREAD ROLLING DEVICE 2 Sheets-Sheet 2 Filed Jan. 6, 1954 INVENTOR.

2,933,955 THREAD ROLLING DEVICE Charles H. Laemmel, Dayton, Ohio, assignor, by mesne assignments, to The Sheflield Corporation, a corporation of Delaware Application January 6, 1954, Serial No. 402,465.

6 Claims. (Cl. 80-6) oil grooves and the like; however, the following discus; f sion and the description of'anillustrative vembodiment-'of the Vinvention has been primarily directed to a thread rolling application. Y v

A large number of the production bolts and screws provided for present-day industry are manufactured by the cold rolling of threads. The work piece provided has a diameter approximately equal to the pitch diameter of the thread desired. The threading rolls are driven by the work and force their threads into the work piece and concurrently squeeze'metal from the workpiece out into the thread rolls. It is extremely important in such thread rolling devices that the -unit be rugged and reliable in operation for precisely forming threads and for a long service life and that the necessary adjustments for a threading operation be made by means which are readily accessible Vand which are simply and rapidly adjustable to secure the correct thread form. It is also importantthat vthe arrangement be suchA that=no unduly large forces result in an-axial direction between the work and the threading device to avoid damage to the threading device or machine and the production of imperfect thread forms.

It is accordingly an object of this invention to provide a device for forming workpieces comprising two cooperating and drivingly interconnected forming rolls, which is simple and rugged in construction, which is adapted for forming a wide range of workpiece sizes and forms and which is quickly set up for a forming op eration by a few, easily made adjustments.

It is a further object to provide a device for rolling threads orthe like whereinl forming rolls are carried for adjustment of the roll .axes toward and from one another for rolling dilferent size workpiece forms and for line adjustment of a workpiece dimension such as, for example, the thread pitch diameter in `thread rolling and wherein the movement of the forming rolls` relative to Vone another can be carried out-.withoutdisturbing A the relative timing between the rolls, thus materially simplifying setup operations.

It is a further object to provide a device of the character referred to wherein a pair of forming rolls are drivingly interconnected, the driving interconnection comprising adjustable means for a precise relative rotation of the rolls through an infinite number of relative relationships within a given range for timing adjustments.

It is a further object to provide a device of the character referred to wherein forming rolls are -drivingly j nlted States Patent() 2,933,955 Patented Apr.' 256, 1969 rice interconnected, including means to adjust the roll timing and wherein the driving interconnection is so arranged that upon `relative movement of the rolls towards and from one'v another their timed relationship is not disturbed whereby once timing is established relative posltioning of the rolls will notdisturb the timed relations 1p. Y Y

It is a further object of this invention to provide a device of the character referred to comprising a body which is carried for limited rocking movement on a mounting member provided for attachment to an existing machine, the device comprising a forming roll rotatable on an axis iixed relative to the body and an adjacent roll carried from the body for bodily movements, the means for adjusting the movements of the one roll being readily accessible at a side of the device remote from the mounting face of the mounting member.

Other objects and advantages of the invention will be apparent from the following description, the appended claims and the accompanying drawings, in which:

Figure 1 is a side view in partial central section of a thread rolling unit embodying the features of the present invention,

Figure 2 is a top view of the unit of Figure 1 with a part-of the threading unit broken away to show a portion lof the driving gear train,

Figure 3 is an end view illustrating the relationship of the threading rolls,r

.Figure 4 is a side view of the unit as viewed from the side opposite to that of- Figure 1,

Figure 5 is a sectional view through the structure whereby the thread unit body is mounted'jfor limited rocking movement and axial sliding, the section being taken onl line S-S of Figure 1,

Figure 6 is a schematic sectional view of the threading unitwith the arm which supports the'adjustably mounted threading roll in a closed position, v

Figures 7 and 8 illustrate structure by which the relative timing of the threading rolls can be adjusted to an infinite number of relationships within a given range of adjustments,

Figure 9 is a sectional view taken along line 9 9 of Figure 2 and illustrates the interconnecting gear train as'viewed from the side,

Figure ll0 isa sectional view on line 10-10 of Figure 9 showing the mounting relationship of the innermost `gears and one embodiment of the means for adjusting the relative timing between the threading rolls,

Figure 11 is a section on line 11-11 of Figure 5 showing in detail the coolant passage arrangement and the clamping means whereby a pivot spindle isclamped to the body of the threading unit for rotation therewith in its rocking movements,

Figure 12 shows the mounting of a threading roll, the means by which the adjustment of one of the rolls towards and from the other is accomplished and the relationship between the threading roll and its driving gear, this iigure being a section taken on the line 12-12 of Figure 9, Y

yFigure 13 is a sectional figure similar to the lower portion of `Figure 10 but illustrating a modification of the means for adjusting the relative timing between the threading rolls wherein the adjustment is made fromjthe side of the unit opposite to that of Figure l0, and

Figure 14 is a view similar to that of Figure 13 illustrating an embodiment wherein the relative timing adjustment can be accomplished from either side of the threading unit.

The features of this invention have 'been illustrated and will be described as embodied in a compact threading unit for mounting on the -movable member of an existing machine for movement toward and from a rgrating cylindrical workpiece for performing threading operations thereon by cold rolling of the workpiece between drivingly interconnected adjacent threading rolls. It should be understood vrthat the features of this inven-j tion are not limited to this precise application butA will have application wherever such rolling or forming operations are being carried on and without being limited to the precise structural form disclosed. r

The illustrated embodiment of this invention comprises a mounting means which includes a mounting plate for lixing upon an existing machine and a mounting niember 11 carried for adjustment along the plate 10. The threading unit body 12 is carried for limited Vrocking movement about the axis of a spindle 14which passes through the mounting member 11 and a rearward extension 22 of the body 12. The body 12 includes side plates 15 and 16 which serve to retain a threading roll 20 in position. A cooperating threading roll 17 is carried from the .body 12 on pivotably mounted arms 18 and 19 for movement toward and from the roll 20. v

The rearward extension 22 of the body 12 has a transverse passage therethrough into which the aforementioned spindle 14 is 'inserted and clamped by means of a tapered clamping element 24 and a clamping screw 25 (see Figure l1). This spindle 14 is freely journaled in the mounting member 11 and it will be seen that upon rocking movement of the body 12 the spindle 14 will rock therewith and will rotate within the mounting member 11. The spindle 14 has a passage 26 extendingce'nitrally along approximately one-half its length which is adapted for connection to a source of coolant under pressure for ushing the workpiece and threading rolls.A As seen in Figure ll the passage. 26` communicates withl an opening through the side wall of the spindle14 and with a passage 27 passing through the body 12. The passage 27 directed toward a point substantially between the threading rolls 17 and 26. The spindle 14 is clamped to the body 12 to prevent its rotation relative thereto so that the transverse opening in the spindle 14'Will not get out of register with the passage 27 in the body 1'2 and cut off the flow of coolant.

The rearward extension 22 of the body 12 is engaged by contacts 28 and 29 mounted for sliding in the mounting member 11. Springs 30 and 33 urge Vcontacts 28 and 29 respectively against extension 22 at opposite vsides of the axis of spindle V14. Screw adjustment 32 threaded within mounting member 11 adjusts the pressure of spring 33 against contact 29 'and screw 'adjustment 3'1 similarly adjusts the pressure of spring 30 against contact '28.

The threading unitas illustrated is adapted for mounting in all positions for threading. The resilient bias furnished bythe contacts 28 and 29 serves to position the body 12 and the threading components which it carries aboutthe axis of the spindle 14 when the unit is clear of the workpiece. The forces exerted by the -springs 30 and 33 are relatively adjusted to position the body 12 so that as the threading unit moves in towards the work one or the other of the threading rolls 17 or 2t) will be contacted rst. During any sequence of threading operations with the same set 'up and same set of threading rolls it is desired that the same one of the threading rolls be consistently contacted initially in order that 'any 'lost motion in the drive between the threading rolls would be taken up in the same direction during each threading operation, thus maintaining timing.

With the pair of contacts 28 and 29 illustrated the unit could be mounted in the position of Figure 1 'or inverted. However, it will be seen that if the unit werey consistently 'mounted in either of these positions a single resilient contact could be provided to' counteract the weight of the threading components and properly vposition the body 12 aboutits rocking axis. v l n Each of the threading vrolls 17 'and '20 has a Vgear car'- ried coaxially therewith and in driving relationship thereto. These roll gears are interconnected through "a drive ing gear train. The mounting of the roll 17 is shown in detail in Figure 12. A pin 34 passes through aligned holes in the arms 18 and 19 and is clamped against rotation by setl screws 36 and 37 accessible from the forward face of the threading unit. The threading roll 17 is mounted for free rotation on the pin 34 and has a radial keyway 38 on one end face. The drive gear 40 is also freely rotatable on the pin 34 and it carries a projecting key 41 formed integrally therewith in the specic embodiment disclosed which mates with the keyway 3S of the threading roll 17. The other threading roll 2i) is similarly mounted between the side plates 15 and 16 of the body unit 12 by means of a pin which is clamped into position by set screws 42 and 44. Ditferent pairs of threading rolls 17 and 20 are necessary when threading workpieces for threads of different pitch diameters and different thread forms. Rolls are readily removed and inserted for mounting into the threading unit of this invention. For example, in removing the threading roll 17 of Figure l2, the set screws 36 and 37 (of Figure 3) are loosened and the pin 34 is slid out of the unit. The drive gear 40 is retained in the unit by a plate 45. The pin 34 is removed, the threading roll 17 is replaced by whatever roll is desired for the subsequent threading operation and the pin 34 is replaced and clamped in position. The roll 20 would be similarly removed and replaced.

As previously mentioned the diameter of a workpiece i' 'should beapproximately equal to the pitch diameter of the finished thread. Theoretically the pitch diameter of the threading rolls should be larger than the pitch diameter of .the nished thread by a multiple equalling the .numberof thread starts on a threading roll. However, it hasbeen-l found in practice that the roll pitch diameter Yshould be smaller thanv this theoretical relationship would 4indicatefby a few thousandths of an inch or less for best threading results.

It will be seen in the specific disclosed embodiment that there are sevengears involved in the drive train between the rolls 17 and 20. Two of the gears are mounted in driving relationship with the threading rolls in the manner previously described. The driving gear mounted coaxially with the roller 20 is identied by the numeral 56.

The gear 51 which meshes directly with roll gear 40 is mounted in the manner shown in Fig. 2. A pin 57 is carried forfreerotation in the arm 18 and is fixed within gear 51. The gear S1 is retainedV in a counterbored section of the arm 18v by the plate 45 which also retains the roll gear 40 when its supporting pin 34, is removed. Gear 52 is a wide face gear which is carried within facing counterbored sections in the arm 18 and thebody member 12. This gear 52 is carried for free rotation upon a pin S8. The pin 58 has a dat head 59 seated in a counterbore in the arm 19 and extends through the 'arm 19, the body 12, rotatably supports the gear 52 and extends Voutward through. lthe arm l18. A nut 60 is threaded on the pin 5S. This pin 58 also serves as the `pivot axis upon which the arms 18 and 19 are pivotably Lmountedy and the nut 60 tightens arms 18 andl 19 against the body 12 restraining them against vfree pivoting Y movement.

l idg 'troll n `The central gear in the drive trainv as illustrated 'is 'indicat'edfat 53 and is VVcarried for its lrotation in la counterbore-formed in one ace of' the body member 12. This v65 v"gear Vifs 'retained within the eo'unterbore in which it 'rotates by' the vside Vplate 15. This central gear 53 'is"rotata'ble on a fixed pinb 68 which extends outward through side 'plate 15 and 'inward a 'limited distance 'into the body Ymember 12. f y A Y YThe threading roll 20 'and its driving gear 56 are mounted'coaxially'in the body member V12'on. the pin 84 which. 'i'sfsupport'ed between the side-plates' '15 and. 16 'in a mannerjequival'ent t the support 'for the upper thread:- 17 in the arms '18 and 19. The gear 55 'which tn'e'she's with the ydriving `'gear 56 for the threading, roll 20 is supported on a pin 85 in a manner equivalent to that for the corresponding gear 51 which meshes with the drive gear 40 for the threading roll 17.

The central gear 53 and the gear 55 are interdriven by a pair of gears (or a split gear) mounted for rotation on a common shaft. These gears are indicated at 87 and 88 mounted on the shaft 89. The gear 8S meshes with the central gear 53 and the gear 87 with the drive gear V55. Provision has been made for causing a relative rotation between the gears 87 and 88 in Vorder to adjust the timing between the threading rolls 17 and 29.

It is seen from Figure that the gears 87 and 88 are carried for rotation in but are restrained against axial movement relative to 'two facing counterbored sections in the side plate and the central portion of the body member 12. The shaft 89 upon which-they'are mounted is carried for rotation and for axial sliding in sleeves 90 and 91 in the side plate 15 and the central portion of the body member 12 respectively. It will be seen from Figures 7 and 8 that the shaft 89 has rradially projecting pins which cooperate withinsubstantially `helical grooves on the inner faces of the gears 87 and 88. As seen in Figure 8 the pins 92 and 94 projecting from the shaft 89 cooperate with helical grooves 95 and 96 formed on the inner surface of the gear 88. A similar arrangement is provided for the gear 87 but only one pin 97 appears in Figure 7 cooperating with the helical groove 98 in the gear 87. `The relative disposition of the pins and grooves can be reversed if expedient. It will-be seen that with this cooperating structure upon rotation of the shaft 89 without axial movement the gears 87 and 88 will rotate concurrently with the shaft. However, should the shaft 89 be slid axially, the gears 87 and 88 will be rotated in opposite directions having the ultimate effect of changing the timing between the threading rolls 17 and 20. This axial movement and the camming relationship between the shaft 89 and the gears 87 and 88 permits an infinite number of relative adjustments between the roll gears 17 and 20 within the range of axial movement of shaft S9 within the threading unit. Any desired relative adjustment between the threading rolls 17 and 20 can be obtained and the accuracy of the relative adjustment is not limited as it would be if serrations or the like Wereemployed between the gears.

Figure'l() illustrates the manner in which the 'shaft 89 is axially slid for the timing adjustment of the lthreading rolls 17 and 20 in one embodiment. In that View it will be seen that the opposite ends of the shaft 89 are engaged by thrust bearing arrangements 99 and 100. At the right hand end of the shaft 89 in Figure l() the thrust bearing 100 is engaged by a spring 101 seated in a counter bore in the right hand plate 16 and extending within the sleeve 91. This spring will resiliently urge the shaft 89 to the left as viewed in Figure 10. The thrust bearing 99 is engaged by a rotatable setting screw 102 threaded within the side plate 15. By rotating the setting screw 102 axial adjustments of the shaft 89 can be accomplished against the resilient bias of the spring 101 in an accurate manner to achieve whatever desired timing relationship is required between the threading rolls 17 and 20. To insurerthat this adjustment is not disturbed a setting screw 104-V engages a brass insert to force itagainst the setting screw 102- and retain it accurately in adjusted position.

It will be noted that in the embodiment illustrated in Figure 10 that theY setting screw 102 is accessible only from the lefthand side of the threading unit as viewed in that figure. In Figure 13 is illustrated a reverse arrangement wherein a spring 101a which is carried in a pocket in a lefthand plate 15a engages the thrust bearing 99 and a screw 102a threaded within a side plate 16a engages the thrust bearing 100. With this arrangement the adjustments are accessible from the other side of the threading unit and this arrangement is usefulwhenever, because of the relative situationV ofmachin'e components, adjustments Vfrom the lefthand side of Figure 10 would be impractica ble. The device can be further adapted for adjustment from either side by the structure shown in Figure 14. In that figure the shaft 89h supporting the gears 87 and 88 has a longitudinal passage therethrough, as does the setting screw 102b. vThe side plate 16b has an opening 105 therein coaxial with the passage through the supporting shaft 89b and the passage in the setting screw 102b. The hex adjustment 106 is therefore accessible from either side of the threading u nit.

The arms 18 and 19 are contacted by setting screws 61 and 62 respectively. These screws are threaded in the laterally extended portions of body 12. The setting screws 61 and 62 serve to xedly adjust the arms `18 and 19 to determine the spacing between the threadingrolls 17 and 20. As seen in Figures 1 and 9 the setting screw 61 is contacted by a' brass plug indicated atV 64 which is urged inward by a screw 65 to positively retain the setting screw 61.against rotation. A similar arrangement is provided for setting screw 62. This arrangement insures that the arms 18 Vand 19 are retained in their ad justed positions in a reliable manner.

In most thread rolling operations there is a resultant thrust along the axis of the workpiece between the workpiece and the threading rolls. In order to relieve this thrust and protect the machine components from damage and to give accurately formed threads on the workpiece the rearward the reward extension 22 of the body 12 is situated on the spindle 14 with some clearance at each side thereof with respect to the mounting member 11. This situation is shown in Figure 5 where also is shown 4the opposed spring pairs 107-108 and 109-110 mounted in pockets formed within the rearward extension 212 of thebody 12 to urge the body 12 toa'centered position with'respect to the mounting member 11. `When the threading unit moves in to contact the Work the work is rotated a given number of revolutions and sufficient clearance is provided to allow a walking movement of the body unit 12 along the length of the workpiece to relieve any thrust which might be produced. In actual operations this Walking movement in either direction varies but a movement on the order one thirty-second of an inch is common. If desired the direction and amount of walking can be controlled by experimental adjustments of the relative timing between the rolls.

It will also be noted (see Figure 12) that there is clearance at each end face of the threading roll 17 with respect to the adjacent members of the threading unit and there is also a limited clearance between the key slot 38 and the mating key 41. A similar relationship exists for the roll 20 and its gear 56. These clearance relationships are provided to allow the rolls 17 and 20 to track one another accurately with some relative freedom in their drive. Thus when a thread form is initiated by the rolls they can relatively shift slightly to track one another and accurately form the thread. This adjustment and free play is necessary to compensate for inaccuracies in the manufacture of the gears and other threading unit components. When the threading unit is moved inrtoward the work one or the other of the adjacent threading rolls is engaged initially and it starts its rotation. Timing is maintained through thegear train'between the threading rolls so that when the second threading roll is engaged by the workpiece both of the rollswill be properly timed. After aV prede- V termined number of revolutions of the workpiece the iininto the mounting member`11 so it will be moved uponV rotation ofthe screw 108. Thus the threading unit can be finely adjusted on its plate which is fixed to the reciprocating member of the existing machine so that upon inward movement of the unit the threading rolls will be moved to a forward extreme position where a line between the roll centers passes through the center line of the workpiece. A pair of rolls is to be performed to selected for the threading operation give the proper pitch diameter on the thread and the proper thread form and these rolis are mounted by removing the supporting pins 34 and 8 4, inserting the threading rolls into the unit, reinserting the pins and fixing themin position by their set screws. The rolls. are mounted inthe threading unit with starting marks on their side faces in opposing relationship. The timing relationship is thus basically established by the associated key structure between each ofthe threading rolls and its drive gear and the interconnecting drive means. Depending upon the diameter of the work to be threaded and the pitch diameter of the thread to be formed, the arms i8 and 19 will be adjusted to relatively position the rolls.

With the present invention the timing between the threading rolls will be maintained during this adjustment. For that purpose an odd number of gears has been mounted between the gear mounted coaxially with the axis of pivoting and the gear carried coaxially with the pivotably mounted threading roll. In the specific embodiment disclosed one gear 51 is so disposed between the gear 52 carried on the pivot axis of the pin S8 and the drive gear 40 which is keyed to threading roll 17. Figure 6 shows the arms adjusted downwardly as viewed inthat figure and it will be seen 'that if the lower, roll Z0 is held stationary as the gear 51 pivots about the fixed gear S2, it will rotate in a clockwise direction. Reference to Figure 9 will show that gears 52 and 40 are of they same diameter, thus concurrently the roll drive gear d@ will rotate in a reverse direction and through an equal angular displacement. Thus the threading roll 17, and its associated driving gear 40, will revolve about the pivot axis of the pin 58 and radii of the roll will remain parallel to their initial positions as the roll is revolved or pivoted about the pivot axis.

A point directly below the roll center in Figure 1 will remain directly below that center when the arm is moved to the position of Figure 6. The threading rolls are closest together at points on their adjacent surfaces lying on a line between their centers. It is these adjacent `surfaces which perform the threading operation. It will be lseen that as the arms 13 and 19 are pivoted in either direction to carry the threading roll 17 toward or from the other threading roll 20, the proper starting points on the threading rolls will shift in opposite directions through equal angles from a line between their centers. The adjacent roll surfaces move in opposite directions during a threading operation and with the starting points effectively shifting through equal angles in opposite directions as one of the rolls is moved toward and from the other timing will be maintained. It should be noted that if the roll drive gear directly rneshed with 1a gear carried coaxially with the pivot axis, or if an even number ofv gears were-interposed between the rollgear :and the pivot axis gear upon movement of one gear toward or from the vother -thezrelative shift between the froll starting points would notbe equal and opposite from a line between'theircenters but would be unequal and would destroyl the roll timing. That is to say the pivotably carried roll in such a situation would not only-move about its pivot axis but would also rotate and the rolls would be in error bythe amount of relative roll rotation. Another vway of `stating the same relationship is that with the present invention the pivotably carried roll does not rotate aboutpits own axis but has a pure revolution about its pivot axis. Because the :rolls do -not rotate is pivotably mounted.

about their own axes and all initially parallel radii be tween the two rolls remain parallel throughout the movement of the pivotably carried roll, the timing is not disturbed. Thus with this invention the rolls can be relatively moved through whatever adjustments are desired without affecting their relative timing;

In the illustrated embodiment only one of the rolls The adjusting setting screws for adjusting the amount of pivoting movement are accessible at the face of the unit which is remote from the face of the mounting plate. Thus in whatever position the unit is mounted these setting screws are readily accessible from one side of the threading unit only, there are only two main screws to be adjusted, and this adjustment can be carried out in a simple and efficient manner.

In setting up the threading unit for. a threading operation first the proper-rolls are selected and mounted in the manner described above. The marks which determine their relative starting position are placed opposite and the keys will establish their relative timing. The arms are then adjusted to position one of the rolls relative to the other. while either a part or a thread gauge is inserted between the rolls until the thread gauge or part will snap in or out between the threading rolls. With the drive and mount arrangement the timing between the rolls is not disturbed during this adjustment. The unit is then mounted on the reciprocable part of an existing machine, for example, and the stroke is adjusted first coarsely by using the adjustments of the machine and then finely by rotating the screw 108 to position the mounting member 11 relatively to the mounting plate 10.

A few yparts are then threaded and the alignment of the threads is noted to see if the thread rolls are properly tracking one another and have a precise accurate relative timing. .If the parts indicate that the threading is not being carried out properlyvand that the timing is in error the shaft 89 is slid axially to relatively rotate the gears 87 and 88 in the drive train to change the timing between the threading rolls and give the proper timing. The adjustment provided by this invention gives an infinite number of relative adjustments of the rolls relative to one another soV that timing can be precisely carried out.

After the relative timing has been properly-established as determined byv inspecting parts produced the arms are then finely adjusted toward and from one another by using the setting -screws 61 andl 62 while gauging the parts produced to determine if the pitch diameter is proper. The relative positionsof the threading rolls 17 and 20 will determine this pitch diameter. It should be emphasized that during this adjustment of the rolls towards and from one another withA the particular roll drive provided by this invention the timing between the gears is not affected and the predetermined matching relationship between the rolls is automatically maintained. Thus adjustments for pitch diameter and roll timing can be carriedout independently. After the setup has been accomplished the threading unit can be used to rapidly produce threads to accurate form.

Because only one forming roll is adjustable in position the roll spacing adjustment can be provided remote from the mounting structure where the adjustment is readily accessible and can besimply carried out. With v the timing automatically maintained lduring relative spac- ,movements of the-.forming rolls the spacing and timing adjustments can .be' carried out readily and Vsimply,'olr1pe without disturbing the other. Because the unit offthis invention is simple and rugged in configuration it is useful for a long service life. The rolls can be simply removed and replaced, and timing and spacing adjustments quickly made, thus adapting this unit for a wide range of workpiece dimensions and forming applications. Y

While the forms of apparatus herein describedA constituted preferredA embodiments of the'invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. An apparatus for imparting a predetermined form on a rotating workpiece comprising a body, a pair of forming rolls, means ixedly carrying one of said rolls for rotation on said body, support means carrying the other of said rolls for pivotal movement about an axis displaced from its axis of rotation and substantially. parallel thereto for spacing adjustment relative to said one roll through a substantial range of relative adjustment to accommodate different size threading rolls andk difierent nominal workpiece diameters, a gear carried coaxially to each of said forming rolls in driving relationship therewith, a gear train drivingly interconnecting the roll gears and maintaining respective radii of the pivotally carried roll continuously parallel to their previous positions during spacing adjustments between the rolls, said gear train comprising a gear carried for rotation about said pivot axis and an odd number of meshing gears between the roll gear of said pivotally carried roll and the gear coaxial with the pivot axis whereby the roll gear of the pivotally carried roll and the gear coaxial with ythe pivot axis rotate in the same direction.

2. A thread rolling unit comprising a body, a pair of threading rolls,l means xedly carrying a first of said rolls for rotation on said body, ar'm means carrying the second'of said rolls and pivotally mounted about an axis displaced from the roll axis and lsubstantially parallel thereto for spacing adjustment relative to said first roll through a substantial range of relative adjustment to accommodate different size threading rolls and different nominal workpiece diameters, a gear carried coaxially to each of said threading rolls in driving relationship therewith; a gear traindrivingly interconnecting the roll gears and maintaining respective radii of the pivotally carried roll continuously parallel to theirl previous positions during spacing adjustment between the rolls, said gear train comprising a gear carried for rotation coaxial to the pivot axis of said arm means, a single drive gear between the roll gear of the pivotally carried roll and the gear coaxial with the pivot axis, and drive means between the gear coaxial with the pivot axis and the first of said threading rolls for driving the adjacent surfaces of the threading rolls in opposite directions and at the same speed during a threading operation.

3. An apparatus for imparting a predetermined form on a rotating workpiece comprising a body, a pair of forming rolls, means carrying said rolls in said body for rotation about spaced axes and for adjustment toward and from one another, said means comprising support means carrying one of said rolls for pivotal movement about an axis displaced from its axis of rotation and substantially parallel thereto, a gear carried coaxially to each of said rolls and in driving relationship therewith, drive means interconnecting the roll gears, said drive means comprising a gear carried for rotation about said pivot axis and means interconnecting the roll gear of said pivotally carried roll and the gear coaxial with the pivot axisV for rotation in the same direction whereby a predetermined matching relationship of the forming rolls is maintained during pivotal movement of said one gear, and adjustable means in said gear train remote from said rolls operable to relatively rotate said forming rolls one with respect to the other.

4. A thread rolling unit comprising a body, a pair of threading rolls, means carrying said rolls in said body threading rolls for rotation about spaced axes and for adjustment tos ward and from one another, said means comprisin'ga support means for carrying one of said rolls for pivotal adjustment about an axis displaced from its axis of rotation, a gear carried coaxially to each of said threading rolls in driving relationship therewith, a gear train drivingly interconnecting the roll gears, said gear train comprising a gear carried for rotation about the pivot axis and an odd number of meshing gears between the roll gear of the pivotally carried roll and the gear coaxial with the pivot axis, said gear train comprising a pair of gears mounted upon a common shaft and held against axial movement in said body, said shaft being mounted, .for rotation and axial sliding in said body unit, carri means cooperating between said shaft and each of said gears for rotation ofsaid gears and said shaft together and for vrelative rotation of said gears in opposite directions upon axial movement of said, shaft within said gears, and manually actuated means cooperating between said shaft and said body for axial adjustments of said shaft and adjustments of the relative timing of the threading rolls.

5. A thread rolling unit comprising a body, a pair of threading rolls, means carrying said rolls for rotation about spaced axes and for adjustment toward and from one another, said means comprising shaft means in said body carrying one of said rolls on an axis fixed against` adjustment with respect to said body and arm means pivoted on the body carrying the other roll for pivotal movement aboutvan axis displaced from its axis of rotation and substantially parallel thereto, a gear carried co'- axial to each of said threading rolls in driving relationship therewith, a gear drive .means drivingly interconnecting the roll gears, including a gear coaxial with said pivotaxis and a single intermediate gear meshing with both the pivotably carried roll gear and the gear coaxial with the pivot axis whereby a predetermined matcl1- `ing relationship is maintained between the threading rolls during the pivotal movement of said other roll.

6. A thread rolling unitl comprising a body, a rigid pair of threading rolls, means carrying said rolls for rotation about adjustably spaced axes, said means comprising a shaft mounted in said body and supporting one of said rolls on an axis iixed with respect to the body and arm means pivoted from said body and supporting the other of said rolls for pivotal movement about an axis displaced from its axis of rotation and substantially parallel thereto, a gear carried coaxially to each of said and in driving relationship therewith, a gear train drivingly interconnecting the roll gears, said gear train comprising a gear carried for rotation about said pivot axis, a single intermediate gear meshing with both the roll gear of the pivotally carried roll and the gear coaxial with the pivot axis whereby a predetermined matching relationship is maintained between the rolls during pivotal movement of said other roll, and three intermeshing gears in said body in driving relationship between the pivot axis gear and the gear coaxial with the lixedly mounted roll, adjustable means in said gear train for relative rotational adjustments of said Ithreading rolls, and adjustment means cooperating between said body and the arm means for adjusting the degree of pivoting movement of said one roll with respect to the other.

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Batchelder Nov. 27, 1956 12 .FOREIGN PATENTS i E German Mar. 9, 19.12: Great Britain Jan. 4, 1923s .Italy Dec. .13, 1938 Great Britain .J an. 20, .1939

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